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What's the best way to hard-cook eggs -- boil them for 15
minutes, or bring them to a boil and let them set for 15 minutes?
According to a recent study, either method can work. But the
second method produces a better product and does a somewhat
better job of inactivating Salmonella enteritidis.
Salmonella enteritidis (SE) is a bacteria found in many
animals, particularly chickens. We now know that the inside of an
egg, once considered sterile, can harbor SE. The contamination
occurs inside the hen before the shell forms. While less than 1
percent of all eggs on the retail market contain the bacteria,
this increases to as much as 8 percent of eggs from infected
flocks. Therefore, it's important to properly handle and cook
eggs.
Researchers at the University of Georgia looked at two
methods of hard-cooking eggs. The Egg Board method is to place
eggs in cool tap water, bring it to a boil, remove the pan from
heat, let it set 15 minutes, then cool the eggs in cold running
water. The common method is to place eggs directly into boiling
water, simmer for 15 minutes, then cool the eggs in cold running
water. Because of the time required for eggs started in cool
water to boil, SE was inactivated sooner for eggs cooked this way
than for those placed directly into boiling water. The Egg Board
method also was less likely to result in cracking.
One problem with translating the results of this study to
Colorado is that boiling water never reaches 212 degrees F here.
The authors did note, however, that the key factor in
inactivating SE was keeping the eggs in boiling water long enough
to solidify the yolk. When we repeated the Egg Board method at
5000 feet with large eggs, it took 24 minutes to bring the water
to a boil. Although the highest temperature reached was only 200
degrees F., the yolks were well solidified after setting for 15
minutes, then cooling in cold running water. More time in
simmering water may be needed with extra large eggs and at higher
elevations.
The Egg Board recommends the following method for hard-
cooking large eggs: Place eggs in a single layer in saucepan. Add
enough cool tap water to come at least 1 inch above eggs. Cover
and bring to a boil. Upon boiling, remove the pan from the
burner, allow eggs to set 15 minutes, then place them under cold
running water until completely cooled. This last step prevents
the yolks from turning green. (This green color occurs when
sulfur produced during cooking adheres to the iron in the yolk.)
Hard-cooked eggs also can be contaminated after cooking. To
keep hard-cooked eggs safe when coloring and hiding them:
- Don't color or hide cracked eggs.
- If you plan to eat colored eggs, use food coloring or
specially made food-grade egg dyes.
- Once eggs are colored, keep them refrigerated in their
cartons. Don't let them sit out.
- When hiding eggs, carefully place them in areas safe from
contact with pets, wild animals, birds, reptiles, insects or
lawn chemicals.
- Finally, to keep eggs safe to eat, the total time for hiding
and hunting eggs should be less than two hours.
Re-refrigerate the found eggs until they are eaten. If
hiding and hunting takes more than two hours, use the found
eggs only for decoration, not for eating.
For more information, contact your local
Colorado State University Extension office.
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